This proposal addresses problems that may result in long term failure of total hip arthroplasties. A study of carcinogenesis in metals and polymers, both in solid and powder form implanted into muscle and rat bone, is performed. Stress analysis of prosthetic devices is performed using finite element techniques. The studies are both two and three dimensional and are directed not only to the state of stress of the prosthetic device but also to the surrounding cement and bone. Studies of metal fatigue include evaluation of cast cobalt chrome, stainless steel, titanium alloys and MP35N. Studies of wear of the polymeric materials including ultra high molecular weight polyethylene and Delrin 150 and the relationship between wear of ultra-high molecular weight polyethylene and its molecular structure is being investigated. Retrospective analysis of failed devices including femoral stem and removed acetabular components are being conducted to understand the mechanisms of failure and their relationship between wear patterns and structure of the ultra-high molecular weight polyethylene in vivo. BIBLIOGRAPHIC REFERENCES: Galante, J., Gachter, A., and Rostoker, W.: Note: MP35N: A Corrosion Resistant, High Strength Alloy for Orthopedic or Surgical Implants; Two-Year Bio-Assay Results. J. Biomed. Mater. Res., 10:829-831, 1976. Rostoker, W. and Galante, J.O.: Some New Studies of the Wear Behavior of Ultra-High Molecular Weight Polyethylene. J. Biomed. Mater. Res., 10:303-310, 1976.